Guide
Compressed Air Pressure Drop: Causes & Solutions
Pressure drop in compressed air systems wastes energy — every 1 bar of unnecessary pressure drop costs about 7% more compressor energy. Learn the causes and how to minimise pressure drop.
7 min readUpdated July 2026
What is Pressure Drop?
Pressure drop is the reduction in air pressure from the compressor discharge to the point of use. Every component in the air system — pipes, fittings, filters, dryers, regulators, and hoses — creates friction that reduces the pressure. The total pressure drop is the sum of all individual losses.
The golden rule: Every 1 bar of unnecessary pressure drop forces the compressor to operate at 1 bar higher pressure, consuming approximately 7% more energy. Reducing pressure drop from 1.5 bar to 0.5 bar saves about 7% of compressor energy.
Acceptable Pressure Drop
| Component | Acceptable Drop (bar) |
|---|---|
| Aftercooler | 0.1–0.2 |
| Mainline filter | 0.05–0.1 (clean) |
| Refrigerated dryer | 0.1–0.2 |
| Desiccant dryer | 0.2–0.4 |
| Distribution piping | 0.1–0.2 |
| FRL (filter/regulator/lubricator) | 0.1–0.2 |
| Hose and connections | 0.1–0.3 |
| Total system | Below 0.5 bar (target) |
Causes of Excessive Pressure Drop
- Clogged filters: The #1 cause. As filters remove contaminants, the element loads up and the pressure drop increases. Fix: replace filter elements when the differential pressure reaches the manufacturer's recommendation (typically 0.3–0.5 bar).
- Undersized piping: Pipe that is too small for the flow creates excessive friction. Fix: replace undersized sections or install a parallel line (loop the system).
- Long hose runs: Flexible hoses have much higher friction than rigid pipe. A 10-metre hose can drop 0.3 bar. Fix: use rigid piping for distribution, minimise hose length at the point of use.
- Too many fittings: Each elbow, tee, and valve adds pressure drop. Fix: design the distribution system with the minimum number of fittings. Use long-radius elbows instead of standard elbows.
- Undersized FRL: A filter/regulator that's too small for the flow creates excessive drop. Fix: verify the FRL is sized for the maximum flow at the point of use.
- Internal corrosion: Rust and scale inside old steel pipes roughen the internal surface, increasing friction. Fix: replace corroded piping or consider aluminium or polymer piping systems.
- Quick-connect couplings: Each quick-connect coupling creates a restriction. Multiple couplings in a line compound the problem. Fix: minimise the number of couplings, use full-flow couplings.
How to Measure
- Install pressure gauges: Place gauges at the compressor discharge, after each major component (aftercooler, dryer, filters), and at the furthest point of use.
- Measure at full flow: Pressure drop is proportional to flow². Measure during peak demand — the drop at low flow is not representative.
- Calculate the total: The difference between compressor discharge and point-of-use pressure is the total system pressure drop.
- Identify the worst components: Measure the pressure drop across each component to find the biggest contributors.
Solutions
- Replace filter elements regularly — install differential pressure gauges to know when to change them
- Upsize undersized piping — or install a parallel loop line
- Use rigid pipe instead of hoses for distribution runs
- Minimise fittings — use long-radius elbows and eliminate unnecessary valves
- Install full-flow quick-connect couplings instead of standard ones
- Consider a ring main distribution system — provides multiple flow paths and reduces pressure drop
- Use aluminium or polymer piping for new installations — smooth interior, no corrosion, lower friction
- Size FRLs for maximum flow, not pipe size — a 25mm FRL on a 25mm line may still be undersized